The present invention relates to an electrical connector to be connected to a twisted pair cable and a method of connecting a twisted pair cable to the electrical connector.
In general, there are two types of twisted pair cable, i.e., an unshielded twisted pair cable (UTP) and a shielded twisted pair cable (STP). The unshielded twisted pair cable is a cable made by twisting a pair of single wires. As compared with a simple parallel cable, the unshielded twisted pair cable is not susceptible to noises from outside and has good noise performance with less noise radiation. Further, the unshielded twisted pair cable is easy to handle and reasonable priced. Accordingly, the unshielded twisted pair has been widely used. However, the unshielded twisted pair cable does not have excellent noise performance in comparison with a coaxial cable. For this reason, the shielded twisted pair cable, which is made by twisting a pair of single wires and coated with a conductive shield so as to improve the noise performance, has also been widely used.
When a conventional electrical connector is connected to an end portion of the unshielded twisted pair cable, end parts of a pair of single wires of the unshielded twisted pair cable are connected to a plurality of terminals of the electrical connector. The terminals are disposed within a housing of the conventional electrical connector, and are arranged away from each other with a specific positional relationship. For this purpose, it is necessary to untwist the pair of single wires at the end portion of the unshielded twisted pair cable. As a result, although the unshielded twisted pair cable has specific characteristic impedance at a high frequency when the pair of single wires is twisted, the specific characteristic impedance tends to increase at a portion where the pair of single wires is untwisted.
In addition, in case of the shielded twisted pair cable, the single wires are untwisted after removing a conductive shield at the end parts to expose the pair of single wires. As a result, although the shielded twisted pair cable has specific characteristic impedance at a high frequency when the pair of single wires is twisted, the specific characteristic impedance tends to increase at a portion where the pair of single wires is untwisted.
As described above, when the single wires are untwisted or the conductive shield is removed, the impedance tends to increase at the portion where the twisted pair cable is untwisted. Accordingly, it is difficult to achieve impedance matching between circuits or devices, which are connected via the conventional electrical connector and the twisted pair cable.
Furthermore, when the single wires are untwisted or the conductive shield is removed, initial noise performance of the twisted pair cable tends decrease at the end portion of the twisted pair cable connected to the conventional electrical connector.
Patent Reference has disclosed a method of adjusting impedance of the twisted pair cable. According to Patent Reference, a pair of untwisted single wires is bundled with a tape or a tube at an untwisted portion of the twisted pair cable.
Patent Reference: Japanese Patent Application Publication No. 2004-71404
According to Patent Reference, in case of a small-sized electrical connector or in case of connecting a plurality of twisted pair cable (a plurality of paired wires) to one electrical connector at small intervals, it is not easy to bundle the untwisted pair of single wires with the tape or the tube. As a result, according to the technique described in Patent Reference, it is difficult to connect the conventional electrical connector to the twisted pair cable in a simple procedure, and it is necessary to take more time for the connection work. Further, it may result in poor yield due to poor attachment of the tape or the tube.
In view of the above-described problems, an object of an invention is to provide an electrical connector and a method of connecting a twisted pair cable to the electrical connector. In the present invention, it is possible to control impedance and maintain noise performance of the twisted pair cable, especially at an untwisted portion of a shielded twisted pair cable. Further, it is possible to easily or securely connect the twisted pair cable to the electrical connector.
Further objects and advantages of the invention will be apparent from the following description of the invention.